Medicine

Methodical instruction for students of (medical faculty)

Methodical Instruction for Students of the 1 Course Medical Faculty

 

LESSON 2 (PRACTICAL – 6 HOURS)

 

Themes: 1. The mechanism of nucleophilic substitution. Properties of carboxylic acids.

2. Stereoisomerism. Heterofunctional compounds. Structure and properties of hudroxyacids.

3. Structure, composition and properties of simple and compound.

 

Aim: To learn chemical properties of carboxylic acids and their derivatives; and properties heterofunctional compound (hydroxyacids and oxoacid); properties of lipids and their biological role; to explain the mechanism nucleophilic substitution;

 

Professional orientation of students:

The knowledge structure and chemical properties of carboxylic acids is necessary for understanding partway processes in human body. Acids and their derivatives are products in a lot of biochemical processes, such as glycolysis, tricarbonic acid cycle, metabolism of lipids. Some of acids are relevant biologically active materials (ansaturation fatty acids).

Heterofunctional compounds are widespread in the nature. They are in fruits and vegetable leafs. Also they are formed in body. The lactic acid is product of transformation glucose (glycolysis) in human body. A malic and citric acid formed in a cycle of tricarboxylic acids, which is also known as citric acid cycle or Krebs' cycle. Hydroxo acids such as: pyruvic acid, acetoacetic acid, oxaloacetic acid, ketoglutaric acid are important in metabolism of carbohydrates.

The lipids are important compounds for human body. They are main structural components of cellular membranes; have protective role; the form, in which is sidetracked and power "fuel" is conveyed.

 

Methodology of Practical Class (900-1200).

Investigation of structure, physical and chemical properties of carboxylic acids and they derivatives. Mechanism of nucleophilic substitution reactions.

Theme1. The mechanism of nucleophilic substitution. Properties of carboxylic acids.

Work 1. The qualitative test for carboxylic acids.

Sshort-chain carboxylic acids react with iron (III) chloride and yellow - red colour precipitate of basic salts is formed: 

Materials. Acetic acid solution, 10 % sodium hydroxide (NaOH) solution, 1 % iron chloride solution (FeCl3).

Protocol. Add in tube:

3 drops acetic acid solution,

2-3 drops of 10 % of NaOH solution,

3 drops of iron chloride solution

It is heated this mixture until boiling, after that yellow-red colour precipitate of iron (III)  hydroxyl acetate is formed. Write equations of this reaction.

Work 2. The qualitative test for an oxalic acid.

Materials. Solid oxalic acid, 5 % calcium chloride solution

Protocol. Add in tube:

Some crystals of oxalic acid

5 drops of water; oxalic acid should be dissolved on water

1 drop of this solution put into microscope slide and

1 drop calcium chloride solution

The white colour crystalline precipitate of calcium oxalate is formed. Crystals of calcium oxalate have the form of envelopes

Work 3. To obtain of ester: ethyl acetate

If acetic acid reacts with some alcohol, so ester is formed:

Materials. Sodium acetate (solid), ethanol, concentrate sulfuric acid.

Protocol. Add in tube:

Some crystals of sodium acetate,

3 drops of alcohol,

2 drops of sulphuric acid.

This mixture is heated to boiling. The ethyl acetate is formed.

Work 4. Hydrolysis of the urea.

Materials. Solid urea, barium water (barium hydroxide solution).

Protocol. Add in tube:

Some crystals of urea

5 drops of barium water

The tube is put on boiling water. After 15-20 min. the litmus paper is a blue and barium water becomes cloudy. Write the reaction of hydrolysis urea.

Work 5.To obtain the biuret and to study a biuret reaction.

Materials. Solid urea, 2 mol/l sodium hydroxide solution, 0,2 mol/l  cupper sulfate solution.

Protocol. Add in dry tube:

Some crystals of urea.

The tube is heating until formed gas (ammonia) and solid: biuret and cyanuric acid.

Mixture should be cool and after that add on tube 15 drops water. Biuret should be dissolve. This solution put on other tube and add:

2 drops of sodium hydroxide solution

1 drop cupper sulphate solution.

The pink-violet colour solution is derived (biuret test). Biuret reaction is the qualitative test on peptide bonds.

Theme 2. Stereoisomerism. Heterofunctional compounds. Structure and properties of hydroxylacids.

Work 6.To determine two carboxylic groups on molecule tartaric acid.

Materials. 15 % tartaric acid solution, 5 % potassium hydroxide (KOH) solution.

Protocol.  Add in tube:

1 drops tartaric acid solution;

2 drops of potassium hydroxide solution,

White crystalline precipitate of potassium hydrotartrate has been formed.

After that add again 4-5 drops of potassium hydroxide solution.

White crystalline precipitate of potassium hydrotartrate has been dissolved and potassium tartaric is formed.

Write equations of reaction

Work 7. To determine two hydroxyl groups in molecule tartaric acid.

Materials. Potassium tartaric solution, which is preparing on 7 work, 10 % sodium hydroxide solution (NaOH), 2 % copper sulfate solution.

Protocol.  Add in two tubes:

2 drops cupper sulfate solution;

2 drops of sodium hydroxide solution,

Add on one of these tubes 1drop potassium tartaric solution, which is preparing on 7 work. All tubes are heated. In first tube, which is potassium tartrate solution is formed blue solution, but on other tube is formed yellow-red colour precipitate.

The blue solution, which formed on first tube is called a Feling’s regent, and is used for determination of glucose in urine.

Work 8. To make calcium citrate and tartrate.

Materials. solid citric acid, solid tartaric acid, 10 % ammonia hydroxide solution, 0,5 mol/l calcium chloride solution. 

a) to prepare calcium citrate.

Protocol.  Add in tube:

Some solid citric acid

10 drops of water, citric acid can dissolve;

10 drops of ammonia hydroxide solution;

5 drops of calcium chloride solution.

Tube with mixture is heated, after 2-3 mins., white colour precipitate has been form in it.

b) to prepare calcium tatrate.

Protocol.  Add in tube:

Some solid tartaric acid

10 drops of water, tartaric acid can dissolve;

10 drops of ammonia hydroxide solution;

5 drops of calcium chloride solution.

After 2-3 mins white colour precipitate has been form in it.

Work 9. To determine free phenyl hydroxyl in salicylic acid.

The reaction between salicylic acid and iron chloride has been used as a qualitative test for the free phenyl hydroxyl. Because in this reaction was made the colour violet derivative salicylic acid.

 

 

 

 

 

 

 


Materials. 5 % solution of iron chloride, crystalline salicylic acid, distilled water.

Protocol. Add in the tube:

some crystal of salicylic acid,

5-6 drops of distilled water (salicylic acid can be dissolve),

1 drop 5 % solution of iron chloride

This solution has been violet colour

Work 10. The hydrolysis of acetylsalicylic acid and .

The acetylsalicylic acid hasn’t free phenolic hydroxyl, because hydroxyl was acelated and if added to acetylsalicylic acid iron chloride wasn’t made the violet colour derivated. But if solution is boiling, that acetylsalicylic acid is hydrolyzed on salicylic acid and acetyl acid.

 

 

 

 


a)

 

 

b)

 

 

Materials. 5 % solution of iron chloride, crystalline acetylsalicylic acid, distilled water.

Protocol. Add in the tube: some crystal of acetylsalicylic acid,

5-6 drops of distilled water (acetylsalicylic acid can be dissolve).

Solution of acetylsalicylic acid is divided into two tubes.

Add 1 drop of 5 % iron chloride solution in one of them. This solution has not violet colour.

Solution in other tube is heating, after that adds 1 drop of iron chloride solution. This solution has been violet colour. Explain outcomes of experience.

Theme 3. Structure, composition and properties of simple and compound lipids.

Work 11. To obtain of fatty acids by soap solution.

Materials. Soap solution, 2 mol/ l sulfuric acid solution

Protocol.  Add in tube:

5 drops of soap solution;

1 drop sulfuric acid solution

The white color precipitate of free fatty acid is formed.

Write the scheme of reaction.

Work 12. Addition reaction to unsaturated fatty acids.

Materials. soap solution, 2 mol/ l sulfuric acid solution, bromine solution.

Protocol. Add in tube:

5 drops of soap solution;

1 drop sulfuric acid solution

3 drops of bromine solution (or potassium permanganate solution)

Solution is colorless after reaction, if unsaturated fatty acids present on solution.

Write the scheme of reaction

Work 13. To prepare of calcium fatty acid salts.

Materials. Soap solution, 5 % calcium chloride solution

Protocol. Add in tube:

5 drops of soap solution;

1 drop calcium chloride solution

The white colour precipitate is formed.

Work 14. To investigate capacity of soap to emulsify fats.

Materials. Soap solution, oil

Protocol. Add in tube:

1 drop of oil;

10 drops of water

This is mixed. An-stability emulsion has been formed, which division in two phases. Add 5 drops of soap solution on mixture; stability emulsion is formed after that.

 

Individual Students Program.

1.     Structure and properties of carboxylic acids

2.     Structure and properties of carboxylic acids, alcohols, aldehydes and ketones..

3.     Benzene, structure and properties.

4.     Phenol, structure and properties.

5.     Fats as esters, their role in the nature.

I. The mechanism of nucleophilic substitution. Properties of carboxylic acids.

1.     Electronic and levis structure of carboxylic group, influencing elertronodonor and electronoaceptor substitutes on acidity of carboxylic acids.

2.     Nomenclature and classification of carboxylic acids.

3.     Physical properties of carboxylic acids.

4.     Chemical properties of carboxylic acids. Reactions of nucleophilic substitution. Formation functional derivative: salts, amides, anhydrides, haloanhydrides, esters. The mechanism of etherification reaction.

5.     Dicarboxylic acids. Decarboxylation reactions of oxalic acid and malonic acid. Biological value of this reaction.

6.     Urea.  Reaction: hydrolysis urea with solution of inorganic acid; making of biuret. Biological role of these reactions.

II. Stereoisomerism. Heterofunctional compounds. Structure and properties of hudroxyacids.

1.     Introduction of optical isomerous. Mirror (optical) isomerism. Asymmetric carbon atom.

2.     Properties of enantiomers.

3.     Nomenclature of Enantiomers: R- and S- convention; D- and L- convention.

4.     Heterofunctional compounds. Hydroxy-acids (alcohol acid), nomenclature, isomerism. Common chemical properties and specific reactions for hydroxyl-acids: dehydratation a-, b-, g- hydroxoacids schedule lactic and citric acids by strong inorganic acids at heating.

5.     Structure and properties of oxoacid: aldoacids and ketoacids.

6.     Value of hydroxo- and hydroxoacids in biochemical processes.

7.     Introduction of optical isomerous. Mirror (optical) isomerism. Asymmetric carbon atom.

8.     Properties of enantiomers.

9.     Nomenclature of Enantiomers: R- and S- convention; D- and L- convention.

10.   Value of hydroxo- and hydroxoacids in biochemical processes.

III. Structure, composition and properties of simple and compound lipids.

1.     Lipids, their functions.

2.      Classification and biological role of lipids.

3.     Fatty acids as a component of lipids. Structure of palmitic (hexadecendioic), stearinic, oleic, linoleic, linolenic and arachidonic acids.

4.     Ttriacylglycerols. Hydrolysis lipids, addition reaction, oxydation.

5.     Physico-chemical constants fats: iodine number, acid number.

6.     Waxs.

7.     Composite lipids: phosphotides: phosphatidylamine, phosphatidylcholine.

8.     Introduction of sphingolipids and glycolipids.

9.     Nonsaponifiable lipids.

10.   Steroids, their biological role. Cholesterol. Bile acids.

 

Seminar discussion of theoretical issues (1230 – 1400 hour).

Test evaluation and situational tasks.

1.      What medium will be in sodium acetate aqueous solution? Why?

2.      What role is of sulfuric acid in an etherification reaction?

3.      What factors influence carboxylic acids activity? Write the formulas of acetic acid, chloracetic acid and trichloroacetic acid. Which of them is the stronger?

4.      Write structural formula of formic acid, acetic acid, propionic acid, oil acid (butanoic acid) valeric acid (pentanoic acid), capronic aci, lauric acid (hexanoic acid), lauric acid (dodecanoic acid), myristic acid (tetradecanoic acid), palmitic acid (hexadecanoic acid), stearic acid (octadecanoic acid), oleic acid, linoleic acid, linolenic acid, arachidonic acid; oxalic acid, malonic acid, succinic acid, glutaric acid, adypinic acid, maleic acid, fumaric acid, phthalic acid, salicylic acid, p-aninobenzoic acid, glycolic acid, lactic acid, tartaric acid, citric acid, malic acid, glyoxylic acid, acetoacetic acid, pyroracemic acid, oxalacetic acid, ketoglutaric acid.

5        Which functional group is in the carboxylic acids?

A.   Carbonyl group

B.   Carboxyl group

C.   Nitro group

D.   Phenyl group

E.    Sulfo group

6.      What product is made in the reaction interaction the carboxylic acids with the alcohol?

A.   Amide.

B.   Anhudride.

C.   Ketal.

D.   Ether.

E.    Ester.

7.      Which product is made in reduction reaction of carboxylic acids?

A.    Alcohol.

B.     Aldehyd.

C.     Ketone.

D.    Phenol.

E.     Ether.

 

Correct answers of test evaluations and situational tasks:

1. The sodium acetate aqueous solution is has been alkaline medium, because it is hydrolyzed in water, and strong base sodium hydroxide and weak acetic acid is formed after that:   

2. Sulfuric acid is catalyst in an esterification reaction.

3. The carboxylic acids activity is depended nature of substitute, which attract with carboxylic group. The stronger is trichloroacetic acid than the chloracetic acid and the acetic acid.

                            

acetic acid        chloracetic acid         trichloroacetic acid

4.

5. B; 6.E; 7 B.

 

Individual student work (1415-1500 hour)  are checked by solving situational tasks for each topic, answers in test evaluations and constructive questions (the instructor has tests & situational tasks).

 

Students must know: 

-         the biological role and chemical properties of carboxylic acids;

-         mechanism of nucleophilic substitution of carbxilic group;

-         methods for the synthesis of the carboxylic acids;

-         the biological role and chemical properties of hydroxo- and oxoacids;

-         stereoisomerism, essence of mirror (optical) isomerism;

-         methods for the synthesis of the hydroxo- and oxoacids;

-         the biological role, structure, composition and chemical properties of lipids.

 

Students should be able to:

-         explain the mechanism chemical conversion of the carboxylic acids;

-         formations of carboxylic acids;

-         explain the mechanism chemical conversion of the hydroxo- and oxoacids;

-         qualitative test on cholesterol.

 

References.

Basic:

1.     David Gutsche, Baniel J. Pasto. Fundamentals of Organic Chemistry. - New Jersey: Prentice -Hall, Inc.Englewood Cliffs, 2005. -1346 p.

2.     Andrew Streltwieser, Jr. Clayton H.  Hcathcocr. Introduction to Organic Chemistry. - New York: Macmillan Publishinc Co., 2006. - 1508 p.

3.      Lewis D. E. Organic chemistry. A modern perspective. – Copyright, 2006. P. 25 – 95

4.     http://intranet.tdmu.edu.ua/data/kafedra/internal/zag_him/classes_stud/biological and bioorganic chemistry/medical/1 course/lesson 2. Carboxylic acids. Lipids. Heterofunctional compounds.

 

Additional:

1.   Andrew Streltwieser, Jr. Clayton H.  Hcathcocr. Introduction to Organic Chemistry. - New York: Macmillan Publishinc Co., 2006. - 1508 p.

2.    Lewis D. E. Organic chemistry. A modern perspective. – Copyright, 2006. P. 25 – 95

 

The methodical instruction has been worked out by: Associate Prof. Dmukhulska Ye. B.

 

 

 

 

 

Methodical instruction was discussed and adopted at the Department sitting

25.06.2013.  Minutes N 11

 

Methodical instruction was adopted and reviewed at the Department sitting

27.08.2013.  Minutes N 1